TORONTO - In an unexpected discovery, Canadian researchers have found a molecule that appears to dramatically boost the ability of standard drugs to kill breast cancer cells in the lab -- and they hope it can be harnessed to counter drug resistance experienced by many women with the disease.
The scientists from Queen's University say the ANK peptide they designed gives drugs like taxol and nocodazole more than triple the punch to kill breast cancer cells compared to the drugs alone.
"Our peptide is not a drug by itself,'' Zongchao Jia, who holds the Canada Research Chair in Structural Biology at Queen's, said Monday from Kingston, Ont. "In the same way that cream flavours coffee to make it taste better, the peptide enhances the effectiveness of the most widely used breast cancer drugs today.''
"This would be particularly useful for those patients who have a serious drug resistance problem,'' he said.
Jia's research team tested the effectiveness of their peptide (a chain of amino acids smaller than a protein) by combining it with a standard cancer drug and adding the mixture to a Petri dish containing breast cancer cells. The scientists also tested the drug alone against the cancer cells.
"And we found that with the peptide, cell death is 3.5 times more than the breast cancer cell (death) without the peptide,'' he said. "So we were very excited.''
However, Jia cautioned that it's early days yet: the results apply only to experiments in the lab. The next step will be to test the peptide-drug combination in lab mice induced to develop human breast cancer tumours. If successful, the scientists would then move onto human testing, but it would likely be some years before this drug "helper'' would become widely available.
Still, the university's technology transfer division is so optimistic about the results -- published online Monday in the journal Cancer Research -- that it has applied for a U.S. patent of the peptide.
Dr. Ian Tannock, a medical oncologist at Princess Margaret Hospital in Toronto, said drug resistance in most types of cancers is a "very big problem -- the central problem as to why we cannot cure many tumours with drugs.''
With advanced (recurrent) breast cancer, about a third to half of women don't respond at all to standard drugs and for those who do, over time, "even if you carry on treatment with the same drugs you started with, the tumour learns to become resistant,'' he said.
Commenting on the Queen's paper, Tannock said the peptide is worth investigating, although it would take several years to develop into treatment.
"It's a long way to go from breast cancer cells in a test tube to expecting that this will necessarily improve the response in people. But it's clearly an interesting idea and it is worth following up.''
Jia said breast cancer patients experience varying degrees of drug resistance, depending on how long they've been taking a particular chemotherapy, the dose they are on and their underlying genetic makeup.
"And this peptide would be able to give them another chance,'' he said. "For those who respond reasonably well, they will do even better; for those who don't respond to this drug treatment ... we greatly hope this will make the current drug more useful by extending its impact to a wider range of people, particularly those with a resistance problem.''
